Meningioma in most cases is a benign tumor that develops from arachnoendothelial cells (dura mater or less often vascular plexuses). Symptoms of neoplasm are headaches, impaired consciousness, memory; muscle weakness; epileptic seizures; malfunction of analyzers (auditory, visual, olfactory). The diagnosis is made on the basis of neurological examination, MRI or CT of the brain, PET. Treatment of meningioma is surgical, involving radiation or stereotactic radiosurgery.
General information
Meningioma is a tumor, most often of a benign nature, growing from the arachnoendothelium of the meninges. Usually the tumor is localized on the surface of the brain (less often on the convexital surface or on the base of the skull, rarely in the ventricles, or in bone tissue). As with many other benign tumors, meningiomas are characterized by slow growth. Quite often it does not make itself felt, up to a significant increase in the neoplasm; sometimes it happens to be an accidental finding with computer or magnetic resonance imaging.
In clinical neurology, meningioma ranks second after gliomas in frequency of occurrence. In total, meningiomas account for about 20-25% of all tumors of the central nervous system. Meningiomas occur mainly in people aged 35-70 years; they are most often observed in women. In children, they are quite rare and account for about 1.5% of all children’s neoplasms of the central nervous system. 8-10% of tumors of the arachnoid meningioma are represented by atypical and malignant meningiomas.
Causes
A genetic defect in chromosome 22 responsible for the development of the tumor has been identified. It is located near the neurofibromatosis (NF2) gene, which is associated with an increased risk of meningioma in patients with NF2. The connection of tumor development with hormonal background in women was noted, which causes a high incidence of meningioma in women. A natural connection between the development of breast cancer and tumors of the meninges has been revealed. In addition, meningioma tends to increase in size during pregnancy.
Also provoking factors of tumor development can be: traumatic brain injury, radiation exposure (any ionizing, X-ray radiation), all kinds of poisons. The type of tumor growth is most often expansive, that is, the meningioma grows as a single node, pushing apart the surrounding tissues. Multicentric tumor growth from two or more foci is also possible.
Macroscopically, a meningioma is a neoplasm of a rounded shape (or less often horseshoe-shaped), most often soldered to the dura mater. The size of the tumor can range from a few millimeters to 15 cm or more. The tumor has a dense consistency, most often has a capsule. The color on the section can vary from gray shades to yellow with gray. The formation of cystic outgrowths is not typical.
Classification
According to the degree of malignancy, there are three main types of meningiomas. The first of them includes typical tumors, divided into 9 histological variants. More than half of them are meningothelial tumors; about a quarter are mixed-type meningiomas and slightly more than 10% are fibrous neoplasms; the remaining histological forms are extremely rare.
The second degree of malignancy should include atypical tumors that have high mitotic growth activity. Such tumors have the ability to grow invasively and can germinate into the substance of the brain. Atypical forms are prone to recurrence. And finally, the third type includes the most malignant or anaplastic meningiomas (meningosarcomas). They differ not only in the ability to penetrate into the substance of the brain, but also in the ability to metastasize to distant organs and often relapse.
Meningioma symptoms
The disease may be asymptomatic and in no way affect the general condition of the patient, up to the acquisition of a tumor of significant size. Symptoms of meningioma depend on the anatomical area of the brain to which it adjoins (the area of the large hemispheres, pyramids of the temporal bone, parasagittal sinus, tentorium, cerebellar angle, etc.). The general cerebral clinical manifestations of the tumor may be: headaches; nausea, vomiting; epileptic seizures; disorders of consciousness; muscle weakness, coordination disorders; visual disturbances; problems with hearing and smell.
Focal symptoms depend on the location of the meningioma. When the tumor is located on the surface of the hemispheres, convulsive syndrome may occur. In some cases, with such localization of meningioma, there is palpable hyperostosis of the cranial vault bones.
When the parasagittal sinus of the frontal lobe is affected, disorders associated with mental activity and memory occur. If its middle part is affected, then muscle weakness, cramps and numbness occur in the lower limb opposite to the tumor focus. Continued tumor growth leads to the occurrence of hemiparesis. Meningioma of the base of the frontal lobe is characterized by olfactory disorders – hypo- and anosmia.
With the development of a tumor in the posterior cranial fossa, problems of auditory perception (hearing loss), impaired coordination of movements and gait may occur. When located in the area of the Turkish saddle, violations occur on the part of the visual analyzer, up to complete loss of visual perception.
Diagnostics
The diagnosis of a tumor is difficult, due to the fact that for many years the meningioma may not manifest itself clinically in any way due to its slow growth. Often, age-related signs of aging are attributed to patients with nonspecific manifestations, so an erroneous diagnosis of dyscirculatory encephalopathy in patients with meningioma is not uncommon.
When the first clinical symptoms appear, a full neurological examination and ophthalmological consultation are prescribed, during which an ophthalmologist examines visual acuity, determines the size of the visual fields and performs ophthalmoscopy. Hearing disorders are an indication for consultation with an otolaryngologist with threshold audiometry and otoscopy.
Mandatory in the diagnosis of meningioma is the appointment of tomographic research methods. MRI of the brain allows you to determine the presence of a volumetric formation, the solidity of the tumor with the dura mater, helps to visualize the state of the surrounding tissues. With MRI in T1 mode, the signal from the tumor is similar to the signal from the brain, in T2 mode, a hyperintensive signal is detected, as well as brain edema. MRI can be used during surgery to control the removal of the entire tumor and in order to obtain material for histological examination. MR spectroscopy is used to determine the chemical profile of a tumor.
CT of the brain allows you to identify a tumor, but is mainly used to determine the involvement of bone tissue and tumor calcinates. Positron emission tomography (PET of the brain) is used to determine the recurrence of meningioma. The final diagnosis is made by a neurologist or neurosurgeon, based on the results of a histological examination of the biopsy, which determines the morphological type of tumor.
Meningioma treatment
Benign or typical forms of meningiomas undergo surgical removal. For this purpose, the cranium is opened and a complete or partial removal of the meningioma, its capsule, fibers, affected bone tissue and the dura mater adjacent to the tumor is performed. Simultaneous plastic surgery of the resulting defect with own tissues or artificial transplants is possible. In the preoperative period, pre-embolization of meningioma is sometimes resorted to.
With atypical or malignant tumors with an infiltrative type of growth, it is not always possible to remove the tumor completely. In such situations, the main part of the neoplasm is removed, and the rest is monitored in dynamics through neurological examination and MRI data. Observation is also indicated for patients with no symptoms; in elderly patients with slow growth of tumor tissue; in cases where surgical treatment threatens complications or is not feasible, due to the anatomical location of the meningioma.
With atypical and malignant type of meningioma, radiation therapy or its improved version − stereotactic radiosurgery is used. The latter is presented in the form of a gamma knife, a Novalis system, a cyber knife. Radiosurgical methods of exposure make it possible to eliminate brain tumor cells, reduce the size of the neoplasm, and at the same time the tissues and structures surrounding the tumor do not suffer. Radiosurgical techniques do not require anesthesia, do not cause pain and do not have a postoperative period. The patient can usually go home right away. Such techniques are not used with impressive meningioma sizes. Chemotherapy is not indicated, since most tumors of the dura mater have a benign course, but clinical developments are underway in this area.
Conservative drug therapy is aimed at reducing brain edema and existing inflammatory phenomena (if they occur). For this purpose, glucocorticosteroids are prescribed. Symptomatic treatment includes the appointment of anticonvulsants (with convulsions); with increased intracranial pressure, surgical interventions aimed at restoring the circulation of cerebrospinal fluid are possible.
Forecast
The prognosis of a typical meningioma with timely detection and surgical elimination is quite favorable. Such patients have a 5-year survival rate of 70-90%. The remaining types of meningiomas are prone to recurrence and even after successful removal of the tumor can lead to death. The percentage of 5-year survival of patients with atypical and malignant meningiomas is about 30%. An unfavorable prognosis is also observed with multiple meningiomas, which account for about 2% of all cases of this tumor.
The prognosis is also influenced by concomitant diseases (diabetes mellitus, atherosclerosis, coronary artery disease – ischemic lesions of coronary vessels, etc.), the age of the patient (the younger the patient, the better the prognosis); tumor indicators – location, size, blood supply, involvement of neighboring brain structures, the presence of previous brain surgery or data on radiation therapy in the past.